The invention relates to a process and catalyst system for the polymerization of dicyclopentadiene.
U.S. Pat. No. 4,400,340 relates to a process for the manufacture of a thermoset homopolymer by combining a reactant stream containing a metathesis catalyst and a second reactant stream containing an activator for the metathesis catalyst, at least one of the streams further containing dicyclopentadiene monomer, to form a reaction mixture which is then injected into a mold where polymerization of the monomer occurs. The catalyst may be a tungsten-containing compound solubilized by the addition of a small amount of a phenolic compound such as phenol, alkylphenols and halogenated phenols, with tert-butyl phenol, tert-octyl phenol and nonyl phenol being preferred. The starting dicyclopentadiene for this process employing an activator-containing metathesis catalyst system must be essentially pure.
U.S. Pat. No. 4,729,976 relates to a process for the bulk polymerization of dicyclopentadiene by contacting it with a catalyst system comprising (i) a tungsten compound which contains a phenyl group carrying a bulky alkyl group and (ii) an organic tin compound containing one hydrogen atom bound to the tin atom. This process has the advantages that the starting dicyclopentadiene need not be essentially pure, and that the catalyst is more stable and less sensitive to oxygen.
The processes described above can be applied in a reaction injection molding (RIM) process. This process involves mixing two or more low-viscosity streams of components of the catalyst system and injecting the combined streams in monomer solution into a mold, where the monomer polymerizes to form a solid infusible mass.
One requirement for a RIM process is that the catalyst system promote a high polymerization rate. Furthermore, it is desirable that the polymerization start at ambient temperature, for example in the range of from 15.degree. to 30.degree. C., so that the compounds of the catalyst system can be mixed without addition of heat.
It is thus an object of the present invention to enhance the rate of polymerization of dicyclopentadiene by providing a more active tin-containing catalyst system.